Relationship between physicochemical characteristics and in vitro digestibility of chestnut (Castanea mollissima) starch

The present study investigated the differences in starch and amylose content among six chestnut cultivars widely distributed in China, as well as the relationship between their physicochemical characteristics and in vitro digestibility. The cultivar and geographical distribution significantly influenced the characteristics of chestnut starch. The starch granule from all six cultivars was round or irregular polygonal in shape, with a particle size that varied from 1 to 20 μm. The amylose content ranged from 22.27 to 29.80% of starch, while the damaged starch was 3.44–11.94%. The volume average particle size of the chestnut starches from the six cultivars varied from 8.33 to 10.24 μm, and the median diameter ranged from 6.82 to 8.69 μm. The short-range order of the six chestnut starches exhibited no significant difference, but their X-ray patterns were different and their relative crystallinity ranged between 19.3 and 27.9%. The resistant starch accounts for 70.1–85.6% of chestnut starch, and was found to be positively correlated with the amylose content. The glycemic index was negatively correlated with the relative crystallinity, indicating that the crystalline structure of starch had a retardant effect on its digestibility.